1. Field of the Invention
This invention relates to a disposable cloth having a solvent pre-saturated therein for cleaning printed circuit assembly equipment.
2. Description of the Prior Art and Brief Summary of the Invention
It is standard practice, in the manufacture of printed circuit boards and electronic assemblies, to use solder. The solder establishes both the physical and electrical connections of individual components to the circuit board. The solder attachment process typically requires flux to accomplish wetting of the metal surfaces to be joined in soldering. This flux is usually a gum rosin derivative. Other similar materials used in circuit manufacture include conductive and resistive inks, polymer thick films epoxies, and solder masks in viscous liquid form. These products are all applied to the circuit assembly via dispensing equipment or screen/stencil printers, or both. Due to the variances in the process, tight registration tolerances, and other factors, this material is not always applied properly; misprints and non-uniformly dispensed material must be cleaned off the assembly prior to re-printing or re-dispensing material on the same PC board or substrate.
A primary object of the present invention is to provide an efficient methodology for cleaning mis-printed assemblies utilizing a non-ozone depleting solvent that is non-toxic and non-flammable and formulated for the chemistry of the materials being cleaned. This solvent is impregnated in a cloth that must be a lint-free non-woven material capable of cleaning the substrate of all material while leaving behind no residue and no lint.
When applying a solvent to a cloth to clean, one may pour solvent onto it, which often results in spillage and waste; or one may use a pump-style dispensing can, which can dispense too much or too little, depending on the operator. Too little solvent on the cloth will result in the substrate not being cleaned completely. Furthermore, some types of solvents will carry contaminants into the PC board material and cause current leakage over time if the finished assembly operates in a humid environment. This can result in catastrophic failure of the assembly and equipment. To counter this, assemblies cleaned in such solvents must be washed in a batch-type cleaner and rinsed with distilled/deionized water. Also, solvent left in the pump can reservoir evaporates into the work environment. Many of these solvent types used contain ozone-depleting CFCs (Chlorofluorocarbons) (ex.: 1,1,1, Trichloroethylene, Xylene, Freon TMS, Acetone) and may have carcinogenic properties as well as being highly flammable.
One of the easiest ways to contact clean an object (i.e. wiping instead of immersion) and insure that the proper amount of solvent is fully saturated in the wipe is to purchase an airtight, resellable canister of disposable cloths with the cleaning solutions saturated therein. Various types of cloths have been impregnated with specific cleaning compounds and have designated tasks for which they will work. For example, there are presaturated cloths for disinfecting bathroom counter tops, cleaning mirrors, and cleaning babies.
A further object of the invention is to provide an improved formulation saturated in a disposable cloth. The cloth is for cleaning flux, solder paste, inks, and adhesives (uncured) from Surface Mount printed circuit boards and electronic assemblies, screens, stencils, tools, squeegees, and benchtops. The impregnated cloth according to the invention is low in odor and toxicity, non-flammable, biodegradable, and environmentally friendly. The specific cleaning composition is non-hazardous and free of CFCs. The composition dries fairly quickly without leaving a residue.
The present invention provides a canister having a number of disposable wipes therein. The wipes are presaturated with a solvent (ROSSTECH 119ME; Rossi Technology Corp.) having the formula C.sub.n O.sub.m H.sub.p wherein n=4 to 9, m=2 to 4, and p=10 to 18. The solvent consists of greater than 95.0% of glycol ethers, and less than 5.0% of alcohols.